July Weather Report

 A modest month in most categories.  Little rain - Hanrahan will be talking about drought in the near future - mostly moderate temperatures; low humidity and calm wind.  I was a bit busy yesterday and will be for the next two days, so this is a draft.  It may get updated later!

Rain

A rather low total amount of rain,75% of which fell in one burst late on 20 July.

The pro-rata estimate of the annual total (now 1110 mm) fell almost uninterruptedly through the month.

The low rainfall contrasts with comments made by colleagues in a weather group, focussed on the Central Tablelands of NSW, who have had a soggy month.  A map of rainfall from the BoM shows the rain shadow of the Great Dividing Range: the darker blue areas got between 200 and 300 mm.  Our fall on the 20th got us a little damper than many East Coast areas.

Temperatures

After a warm start the anomaly settled down to around +0.5C.  This was a mixture of maxima and minima being slightly above expectations.

The comparison of current and average extremes using BoM shows the current vaues fluctuating around the average with warm spells at the start of the month and from the 26th.

The next chart compares the extremes from my weather station with those from the BoM site.  As usual the maximum is usually a little higher while the minimum varies more but averages out to similar.

Minimum Temperatures

A little above average but well below last year when continual cloud kept the nights warm.

Maximum temperatures

The following was written using the old data series. "The two warm patches resulted in an average maximum well above the long term average.  That is affected by the long term value being largely driven by BoM values which are mitigated by a cooling sea breeze on many days.  I am working out how to allow for that and will post about the outcome in the near future."

I have since revised the historic data series to make it more compatible with observations from my Weather Station. https://docs.google.com/document/d/1X5Y76N84kLgDC2XgXWmLWFPFxLd8hbHTBlyqG10IyRQ/edit?usp=sharing.  As a result the historic average maximum temperature in July rose by 0.6C, but the July 2021 average maximum is still above the average.

A long term series for July Average maxima, using the revised data.  While the linear trend slopes upwards the value of R2 shows this not to be significant.

Humidity

Quite a moderate month with some low 0900 hrs values being the most notable.   is 

Both time readings were on average less humid than expected and especially so in comparison the the very wet 2020.

Wind

The month could almost rate as calm with only one notable daily run.